The surface key is used to provide additional information about the physical surface of roads/footpaths and some other features, particularly regarding material composition and/or structure. Originally concerned about the surface in relation to transport and sports and more commonly used on linear features it is now increasingly used with certain areas of type natural=*. For broader descriptions of surfaces see Landcover.

For roads for motor vehicles there there is normally an assumption that the surface is surface=paved unless otherwise stated. Paved in OpenStreetMap is non-specific and may cover sealed, tarmac, asphalt, bitumen. surface=unpaved is treated as the opposite of paved. More specific tags can used used for surfaces which are normally classified into paved or unpaved for routing purposes. Navigation software should assume that roads-that-are-not-paved will have slower driving speed (and therefore longer driving time) and may be impassable in some weather conditions.

smoothness=* is also an important surface property and refers to surface regularity/flatness, regardless of material. May be especially useful for roller blades and similar purposes.

tracktype=* is also an important surface property and refers to surface firmness, regardless of shape.

highway=* ways should ideally always be tagged with surface (and/or with tracktype=*) given that there is no default for such paths.

Rendering software convention varies, but generally roads-that-are-not-paved are shown in a different colour but same width as their paved cousins or use the same colour but are dashed. Rendering of road surface in standard OSM style is a complicated subject.

In some cases when other tags are not sufficient to describe the road conditions good enough the use of smoothness=* and maxspeed:practical=* can be considered. maxspeed:practical=* can be useful in situations where other tags are not sufficient to describe what kind of traveling speed could be reasonably expected. If there is one good surface=unpaved road, where practical speed is 60 km/h, and a second bad road with concrete:lanes surface allowing a practical speed 10 km/h, users or routing software could be misguided to choose the second road for routing, because by default paved roads are assumed to allow much higher speeds than unpaved roads.

Cement based concrete, forming a large surface, typically cast in place and may have predetermined breaking joints. For pre-fabricated plates, please use concrete:plates or concrete:lanes if you know how the concrete is laid out and one of these tags fits.

Long, narrow concrete elements for a two-tracked vehicle (motorcars) so that the tires always hit the concrete. There might be sand, ground, grass, pavers, asphalt, etc. in between them. Note that if you tag a single-tracked way you just use concrete, since there are no lanes.

A relatively smooth surface paved with artificial blocks (block pavers, bricks) or natural stones (flagstones), with a flat top. The gaps between individual paving stones are very narrow, either because the stones have a perfectly regular shape (rectangular, or any surface-filling shape) or because they have been carefully selected, fitted and placed in order to form an even, closed surface.

A highway feature is predominantly unsealed along its length; i.e., it has a loose covering ranging from compacted stone chippings to earth. Unpaved roads may, in aerial imagery, show evidence of water along their course; in such circumstances, the waterway should not be tagged as a stream, though it might appear as such. This value gives only a rough description; use a more precise value if possible.

A mixture of larger (e.g., gravel) and smaller (e.g., sand) parts, compacted (e.g., with a roller), so the surface is more stable than loose gravel. Used, for example, for park paths, better tracks, some service ways, … Best sort of ways below paving with asphalt, concrete, paving stones. Sometimes known as water-bound macadam. Mixture and compacting leads to more grip and stability.

A multilayer pavement with a stone or gravel basis and a topmost surface of firm, granular grit, basalt or quartz, as invented by the Roman empire. Easy to walk, jog, cycle or ride on. In hilly areas mostly with drainage channels and concave cross-section for proper water shedding. Motorized vehicles will not move stones if the way is maintained properly, and bicycles tires will not leave any imprints at least in dry weather. If the topmost surface is heavily eroded or loose gravel aggravate going please use gravel instead.

Broken/crushed rock with sharp edges, known as ballast on railways. Usually loosely arranged. Typical size for road and surface construction range between 4 and 8 cm. Gravel can be used as a ground-layer for compacted.

Pebbles are stones rounded by waves or river flow. Typical size range from 2 to 8 cm. Describing a surface in OSM they are loosely arranged. Like gravel pebbles can be used as a building part of compacted.

Probably very similar to ground. Like all this, it is prone to erosion and therefore often uneven. Gravel is sometimes mistakenly called dirt. Some compacted roads are sometimes called dirt too, please consider the definition of compacted.

A sort of permeable paving using regular cell structure, where the voids in this structure enable rainwater to drain into the ground and the structure itself increases the load bearing capability. Often used for parking lots or infrequent used ways like for emergency-vehicles.

It is a mostly 30cm thick one layer surface pavement. It consits out of natural gravel (or recycling materials for construction) and is mixed with soil. On top grasses and herbs are planted. In the end it is a green but also compacted surface with a high level of water infiltration. It is used for example for parking areas, fairgrounds or campsites.

No special surface, the ground itself has marks of human or animal usage. This value gives only a rough description; if possible, use a more precise value such as grass, clay, sand, earth, gravel or pebblestone.

Similar to ground but most of the year wet which gives a soft ground with low carrying capacity. Mostly found on wetland like swamps or in tidal areas. Sometimes also found on slopes draining onto a way.

Metal grids are often used as a surface on industrial-style bridges or stairs. When wet, the surface can become very slippery, especially for bikes. The surface can also be unsuitable for dogs, due to the sharp edges and the look-through effect.